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United States Patent |
5,771,696
|
Hansel
,   et al.
|
June 30, 1998
|
Internal manifold fuel injection assembly for gas turbine
Abstract
A gas turbine engine fuel injection assembly includes a combustor case
surrounding a combustor having a dome. An arcuate manifold is disposed
inside the combustor case adjacent to the dome, and includes a plurality
of fuel injectors disposed in flow communication therewith for receiving
fuel for injection into the combustor. An inlet stem is joined in flow
communication with the manifold for channeling fuel thereto, and includes
an inner fitting disposed in a mounting port in the combustor case. A
mounting adaptor is joined to the combustor case at the mounting port, and
circumferentially engages the inner fitting to restrain torsional movement
thereof. An outer fitting extends in the adaptor and engages the inner
fitting in flow communication therewith for supplying fuel thereto.
Inventors:
|
Hansel; Harold R. (Mason, OH);
Cook; George E. (Cincinnati, OH)
|
Assignee:
|
General Electric Company (Cincinnati, OH)
|
Appl. No.:
|
734164 |
Filed:
|
October 21, 1996 |
Current U.S. Class: |
60/739; 60/746 |
Intern'l Class: |
F02C 007/22 |
Field of Search: |
60/39.31,39.32,39.36,734,739,746
|
References Cited
U.S. Patent Documents
2526410 | Oct., 1950 | Price | 60/739.
|
2676461 | Apr., 1954 | Gove | 60/739.
|
2686401 | Aug., 1954 | Newcomb | 60/739.
|
3516252 | Jun., 1970 | Udell et al. | 60/739.
|
3643430 | Feb., 1972 | Emory, Jr. et al. | 60/39.
|
3879940 | Apr., 1975 | Stenger et al. | 60/39.
|
4305255 | Dec., 1981 | Davies et al. | 60/741.
|
4441323 | Apr., 1984 | Colley | 60/737.
|
4467610 | Aug., 1984 | Pearson et al. | 60/739.
|
5316346 | May., 1994 | Maurer | 285/23.
|
Primary Examiner: Casaregola; Louis J.
Attorney, Agent or Firm: Hess; Andrew C., Scanlon; Patrick R.
Claims
Accordingly, what is desired to be secured by Letters Patent of the United
States is the invention as defined and differentiated in the following
claims:
1. A gas turbine engine fuel injection assembly comprising:
an annular case;
an annular combustor disposed coaxially inside said combustor case, and
having a dome;
an arcuate fuel manifold disposed inside said combustor case adjacent to
said dome, and having a plurality of circumferentially spaced apart fuel
injectors disposed in flow communication therewith for receiving fuel
therefrom for injection through said dome;
an inlet stem having a distal end joined in flow communication with said
manifold for channeling fuel thereto, and having an inner fitting at a
proximal end thereof disposed at a mounting port in said combustor case;
a mounting adaptor fixedly joined to said combustor case at said mounting
port and circumferentially engaging said inner fitting;
means for restraining torsional movement of said inner fitting; and
an outer fitting extending in said adaptor and threadingly engaging said
inner fitting in flow communication therewith for supplying fuel thereto.
2. An assembly according to claim 1 wherein:
said inner fitting includes a tubular shroud;
said adaptor includes a mounting flange fixedly joined to said combustor
case, and an integral tubular sleeve coaxially surrounding said shroud;
and
said means for restraining includes a first plurality of splines formed on
said tubular shroud, and a second plurality of splines formed on said
tubular sleeve, said second plurality of splines being complementary with
said first plurality of splines for engagement therewith.
3. An assembly according to claim 2 further comprising means disposed
radially between said manifold and said combustor case for supporting said
manifold axially and radially while permitting unrestrained differential
radial movement therebetween.
4. An assembly according to claim 3 further comprising:
first means for sealing said adaptor to said combustor case against
differential pressure across said combustor case; and
second means for sealing said inner fitting to said adaptor against said
differential pressure across said combustor case.
5. An assembly according to claim 4 wherein said inner fitting includes a
ballnose sealingly engaging said outer fitting for channeling fuel into
said inlet stem, with said shroud being fixedly joined to said ballnose
and spaced outwardly therefrom to define an annular slot therearound for
receiving a portion of said outer fitting.
6. An assembly according to claim 5 wherein said outer fitting includes a
ferrule disposed in flow communication with said ballnose, and a
cooperating threaded collar disposed in part in said slot for threadingly
joining said outer fitting to said inner fitting at said ballnose.
7. An assembly according to claim 6 wherein said collar includes internal
threads, and said ballnose includes external threads engaging said collar
internal threads for torsionally joining together said outer and inner
fittings.
8. An assembly according to claim 6 wherein:
said first sealing means comprise a first ring seal mounted in compression
between said mounting flange and said combustor case; and
said second sealing means comprise a second ring seal mounted in
compression between said shroud and said sleeve.
9. An assembly accordingly to claim 8 wherein said second ring seal is
disposed inside said sleeve between said mounting flange and said sleeve
splines.
10. An assembly accordingly to claim 6 wherein said manifold supporting
means comprise a plurality of circumferentially spaced apart tubular lugs
extending radially outwardly from said manifold; and
a plurality of pins fixedly mounted to said combustor case and extending
radially inwardly in part into respective ones of said lugs.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to gas turbine engines, and, more
specifically, to fuel systems therefor.
A turbofan gas turbine engine includes in serial flow communication a fan,
compressor, combustor, high pressure turbine powering the compressor, and
a low pressure turbine powering the fan. When used with an augmenter or
afterburner following the low pressure turbine, the engine also includes
an annular fan bypass duct which channels a portion of the fan air
downstream over the combustor and to the afterburner for providing cooling
air thereto.
The bypass duct is defined by an annular radially outer casing and an
annular combustor case spaced radially inwardly therefrom. The combustor
case surrounds the annular combustor and is suitably joined at its
upstream end to a diffuser mounted at the discharge end of the compressor.
The diffuser receives high pressure discharge air which is fed to a fuel
injection assembly for mixing with fuel and being burned in the combustor
for generating hot combustion gases. The compressor discharge air
surrounding the combustor is bounded by the combustor case which is
suitably sealed for preventing leakage of the high pressure air into the
fan air channeled through the bypass duct which is at a substantially
lower pressure, on the order of several hundred psi lower.
Typical fuel injectors have long stems, with a mounting flange at the
radially outer end, and a fuel injector or tip at the radially inner end.
The injector is disposed in a corresponding air swirler mounted to the
upstream or dome end of the combustor. The mounting flange is sealingly
bolted to the combustor case through a corresponding port therefor to
prevent leakage of the high pressure compressor discharge air from the
combustor case and into the fan bypass duct.
In a typical annular combustor, there are a substantial number of
individual fuel injectors and corresponding stems mounted into
corresponding air swirlers. In a double dome combustor, two annular rows
of fuel injectors and corresponding air swirlers are used which increases
the number thereof. Each individual fuel injector and air swirler must be
accurately located in the combustor dome to maximize combustion efficiency
for obtaining acceptable specific fuel consumption (SFC) and exhaust
emissions. Both SFC, and in particular NOx emissions may be decreased by
increasing the number of fuel injection locations to more uniformly inject
and mix the fuel and air into the combustor for combustion.
However, increasing the number of fuel injectors correspondingly increases
the difficulty of accurately positioning each fuel injector in the
combustor dome. And, more complex shapes of the fuel stems such as
S-shaped stems, which must be assembled through the combustor case also
increases the difficulty of accurately positioning the fuel injectors in
the combustor dome.
Since each fuel injector and stem are individually manufactured, they are
subject to typical manufacturing tolerances which vary randomly from
injector to injector by several mils for example. Since each fuel injector
is relatively long from its mounting flange to its injector tip, it is
difficult to accurately manufacture and assemble the individual fuel
injectors for maintaining accurate final positions thereof in the
combustor. Accordingly, further improvements in SFC and NOx are still
possible by providing further improvements in fuel injector mounting
design.
SUMMARY OF THE INVENTION
A gas turbine engine fuel injection assembly includes a combustor case
surrounding a combustor having a dome. An arcuate manifold is disposed
inside the combustor case adjacent to the dome, and includes a plurality
of fuel injectors disposed in flow communication therewith for receiving
fuel for injection into the combustor. An inlet stem is joined in flow
communication with the manifold for channeling fuel thereto, and includes
an inner fitting disposed in a mounting port in the combustor case. A
mounting adaptor is joined to the combustor case at the mounting port, and
circumferentially engages the inner fitting to restrain torsional movement
thereof. An outer fitting extends in the adaptor and engages the inner
fitting in flow communication therewith for supplying fuel thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, in accordance with preferred and exemplary embodiments,
together with further objects and advantages thereof, is more particularly
described in the following detailed description taken in conjunction with
the accompanying drawings in which:
FIG. 1 is a schematic, partly sectional axial view of an exemplary turbofan
gas turbine engine including a fuel injection assembly in accordance with
one embodiment of the present invention for providing fuel to a combustor
therein.
FIG. 2 is a radial, upstream facing view of the fuel injection assembly
illustrated in FIG. 1 and taken generally along line 2--2.
FIG. 3 is an enlarged, axial sectional view of a portion of the fuel
injection assembly illustrated in FIG. 2 and taken along line 3--3 showing
an exemplary fuel inlet stem extending from a combustor case to an arcuate
fuel manifold.
FIG. 4 is an exploded view of exemplary elements of the fuel injection
assembly illustrated in FIG. 3 showing assembly thereof to the combustor
case.
FIG. 5 is a radially inwardly facing top view of the mounting end of the
fuel inlet stem illustrated in FIG. 4 and taken generally along line 5--5.
FIG. 6 is a radially outwardly facing view of a mounting adaptor disposed
between the inner fitting and a cooperating outer fitting illustrated in
FIG. 4 and taken generally along line 6--6.
FIG. 7 is an enlarged, sectional view of a mounting arrangement for the
manifold illustrated in FIG. 2 and taken generally along line 7--7 in
accordance with an exemplary embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Illustrated schematically in FIG. 1 is a portion of an exemplary turbofan
gas turbine engine 10 which is axisymmetrical about an axial or
longitudinal centerline axis 12. The engine includes in serial flow
communication a fan 14, a compressor 16, diffuser 18, combustor 20, high
pressure turbine 22a which powers the compressor 16 through a
corresponding drive shaft, and a low pressure turbine 22b which powers the
fan 14 through a corresponding drive shaft.
An annular combustor casing or case 24 surrounds the combustor 20 and
diffuser 18 and receives pressurized discharge air 26 from the diffuser
18. The combustor case 24 is spaced radially inwardly from annular outer
casing 28 and defines therebetween an annular bypass duct 30 which extends
from the fan 14 for receiving a portion of the fan air 32 and channeling
it downstream past the combustor 20 to a conventional augmenter or
afterburner (not shown).
These components of the engine 10 are conventional in structure and
function. In accordance with one embodiment of the present invention, a
fuel injection assembly 34 is incorporated in the engine 10 for more
accurately injecting fuel into the combustor 20 for decreasing both SFC
and NOx emissions.
More specifically, the combustor 20 includes radially outer and inner
annular liners 20a and 20b joined together at upstream ends thereof to a
conventional annular dome 20c. The combustor 20 may take any conventional
form including the double dome combustor illustrated in FIG. 1, or a
single dome combustor (not shown). In the exemplary double dome embodiment
illustrated, two annular rows of circumferentially spaced apart
conventional air swirlers 36 are suitably mounted to the dome 20c
axisymmetrically around the engine centerline axis 12. Each of the
swirlers 36 includes respective rows of stator vanes which swirl the
compressed air 26 into the combustor 20 in a conventional manner. The fuel
injection assembly 34 provides fuel 38 through individual ones of the
swirlers 36 which is mixed with the compressed air and suitably ignited
for generating hot combustion gases 40 which flow downstream through the
combustor 20 and in turn through the turbines 22a, b for powering the
compressor 16 and fan 14, respectively.
In accordance with the present invention, the fuel injection assembly 34
includes the upstream portion of the combustor case 24, with the annular
combustor 20 being disposed coaxially therein, with the combustor dome 20c
being spaced axially downstream from the diffuser 18 at the upstream end
of the combustor case 24. An arcuate, first or radially outer fuel
manifold 42 is disposed inside the combustor case 24 adjacent to the
combustor dome 20c and includes a plurality of circumferentially spaced
apart, axially extending fuel injectors or tips 44 disposed in flow
communication with the manifold 40 for receiving the fuel 38 therefrom for
injection through the dome 20c and the swirlers 36 for producing a
suitable fuel and air mixture for combustion in the combustor 20.
At least one, and preferably a plurality of inlet stems 46 are disposed in
flow communication with the manifold 42 for channeling fuel thereto. As
additionally shown in FIG. 2, a substantially identical second or radially
inner manifold designated 42B is disposed coaxially with the first
manifold 42 and is supplied with fuel through corresponding inlet stems
designated 46B. The first manifold 42 and injectors 44 thereof supply fuel
to the outer swirlers 36, while the second manifold 42B and fuel injectors
44 thereof supply fuel to the radially inner swirlers 36. Accordingly, the
two manifolds 42, 42B may be substantially identical in structure and
function, with suitable configurations for supplying fuel to the outer and
inner swirlers 36.
Although the inner manifold 42B may be independently mounted like the first
manifold 42, in the preferred embodiment illustrated in FIG. 1 it is
suspended from the first manifold 42 by suitable radial straps 48
extending therebetween. Since the manifold arrangements are substantially
identical in structure and function, the following description is specific
to the first manifold 42, with it being understood that the second
manifold 42B and its cooperating components may be identically configured.
The manifold 42 and cooperating stem 46 are illustrated in more
particularity in FIG. 3 in accordance with an exemplary embodiment of the
present invention. The manifold 42 and stem 46 may have any suitable
double-wall design for carrying fuel through the center thereof and
providing an insulating dead air space between the inner and outer walls
for providing heat insulation in a conventional manner. The outer walls of
the manifold 42 and stem 46 therefore define heat shields surrounding the
inner walls which carry the fuel. The individual fuel injectors 44 may
take any conventional configuration and are suitably joined in flow
communication with the manifold 42 for receiving the fuel 38 therefrom and
injecting the fuel through respective ones of the swirlers 36 illustrated
in FIG. 1.
The manifold 42 is arcuate since it extends circumferentially around the
centerline axis 12 of the engine as illustrated in FIG. 2, and in the
preferred embodiment is a continuous annular member. It may be formed of
suitable segments brazed or welded together to form the complete ring.
Although a single one of the fuel stems 46 may be used for channeling the
fuel 38 into the manifold 42, preferably two fuel stems 46 disposed about
180 degrees apart are provided to channel fuel into the manifold 42 at two
circumferential locations from which it is circumferentially distributed
around the manifold 42 into all of the fuel injectors 44 attached thereto
around its circumference.
By mounting the manifold 42 internal to the combustor case 24 and directly
adjacent to the combustor dome 20c, the individual fuel injectors 44 may
be made relatively short in length and relatively simple in configuration
for substantially improving the accuracy of position of the individual
fuel injectors 44 in their respective air swirlers 36. The annular
manifold 42 provides a common reference support from which the individual
fuel injectors 44 are fixedly attached, and therefore the individual
relatively short fuel injectors 44 may be more accurately positioned in
space relative to each other and in turn relative to the combustor 20. As
opposed to conventional individually mounted fuel injectors and
corresponding fuel stems, the common manifold 42 and attached fuel
injectors 44 provides substantially improved positional accuracy for
decreasing SFC and NOx emissions during operation.
However, since the manifold 42 is now positioned inside the combustor case
24 adjacent to the upstream end of the dome 20c, and is in the preferred
form of a continuous ring, it requires special mounting to the combustor
case 24 to avoid or reduce undesirable reaction stress therein during
assembly, and preventing the undesirable leakage of the high pressure
compressor discharge air 26 from the combustor case 24 into the lower
pressure fan bypass duct 30 during operation. As indicated above, the
differential pressure between the inside of the combustor case 24 and the
outside thereof in the bypass duct 30 may be several hundred psi requiring
effective sealing for channeling the fuel through the combustor case 24.
More specifically, and referring again to FIG. 3, the inlet stem 46 is
suitably fixedly joined at its distal end to the manifold 42 in flow
communication therewith, and includes a first, radially inner fuel fitting
50 at its proximal end disposed at a suitable mounting port 52 extending
radially through the combustor case 24.
A tubular mounting adaptor 54 is suitably fixedly joined to the combustor
case 24 at the mounting port 52, and circumferentially engages the inner
fitting 50 in accordance with the present invention to restrain torsional
movement thereof. In the preferred embodiment, the manifold 42 and its
attached stems 46 is assembled or positioned inside the combustor case 24
and is not accessible from outside the combustor case 24 during the
assembly process. Accordingly, the inlet stem 46 is hidden below the
mounting port 52 and cannot be temporarily secured by a conventional
wrench for completing the fuel connection thereto. The mounting adaptor 54
engages the inner fitting 50 as described in more detail hereinbelow so
that a suitable radially outer or second fuel fitting 56 may be sealingly
attached to the inner fitting 50 in flow communication therewith for
supplying fuel thereto. The outer fitting 56 is suitably joined to fuel
supply conduit 58 which supplies fuel from a suitable fuel supply (not
shown) in the engine 10.
In order to allow the outer fitting 56 to be torsionally threaded to the
inner fitting 50 without damaging the inaccessible fuel stem 46, the
mounting adaptor 54 is suitably splined to the inner fitting 50 to
restrain or react torsional loading as the outer fitting 56 is tightened.
The inner fitting 50 as shown in FIG. 3 preferably includes a tubular
shroud 50a having a plurality of circumferentially spaced apart axially
extending splines 50b. The splines 50b are preferably disposed at the
bottom end of the inner fitting shroud 50a on its external surface and are
axial relative to the fitting 50 itself, and extend radially relative to
the engine centerline axis 12.
The adaptor 54 includes a tubular mounting hub or flange 54a which is
fixedly joined to the combustor case 24 by a plurality of
circumferentially spaced apart fasteners in the form of machine screws 60.
The adaptor 54 also includes an integral tubular sleeve 54b fixedly joined
to the flange 54a at the inner diameter thereof, and extends radially
inwardly through the mounting port 52. The sleeve 54b coaxially surrounds
the complementary shroud 50a, and includes a plurality of
circumferentially spaced apart axial splines 54c spaced circumferentially
therearound. The sleeve splines 54c extend axially relative to the sleeve
54b itself, and radially relative to the centerline axis of the engine.
The sleeve splines 54c are complementary with the shroud splines 50b for
engagement therewith to restrain torsional movement of the shroud 50a and
in turn the inner fitting 50.
The assembly of the manifold 42 and attached fuel stems 46 with
corresponding inner fittings 50 to the combustor case 24 is illustrated in
exploded view in FIG. 4. Since the manifold 42 is a full ring, it is
translated axially forwardly inside the empty combustor case 24 into
position under the corresponding mounting ports 52 which are radially
aligned with the two corresponding inner fittings 50. The mounting
adapters 54 are inserted radially inwardly through their respective
mounting ports 52 so that the cooperating splines 50b and 54c engage each
other.
The shroud splines 50b are disposed on the external surface of the shroud
50a as illustrated FIG. 4, and in more particularity in FIG. 5. The sleeve
splines 54c are preferably internal splines at the bottom end of the
adaptor 54 as illustrated in FIG. 4, and in more particularity in FIG. 6.
Also shown in FIG. 6 are three exemplary arcuate slots 54d through which
the fasteners 60 extend for fixedly mounting the adaptor 54 to the
combustor case 24 as illustrated in FIG. 3. The slots 54d allow the
adaptor 54 to be aligned over the corresponding inner fitting 50 so that
the respective sleeve splines 54c engage the shroud splines 50b. The slots
54d have suitable circumferential extent so that the corresponding
fasteners 60 may be inserted therethrough without requiring rotational
movement of the adaptor 54. In this way, the adaptor 54 may be fixedly
attached to the combustor case 24 without imposing any torsional load or
twist on the individual inlet stems 46.
With the mounting adaptor 54 thusly engaging the inner fitting 50, the
outer fitting 56 may then be radially inserted downwardly through the
adaptor 54 to threadingly engage the inner fitting 50 to provide a sealed
joint thereat. More specifically, and referring to FIG. 3, the outer
fitting 56 in this exemplary embodiment includes a tubular ferrule 56a
suitably fixedly joined to the supply conduit 58 by brazing or welding
thereto for example. The inner fitting 50 includes a complementary
ballnose 50c which sealingly engages the outer fitting 56 at the ferrule
56a for channeling fuel into the inlet stem 46. The ferrule 56a defines an
outlet of the supply conduit 58, with the ballnose 50c defining an inlet
to the stem 46, and may have any conventional engagement surfaces for
effecting a suitable fluid seal thereat upon tightening of the outer
fitting 56 to the inner fitting 50.
The outer fitting 56 also includes a cooperating threaded collar 56b which
extends radially inwardly into the inner fitting 50. The collar 56b
preferably includes internal threads 56c at its bottom end, and the
ballnose 50c preferably includes complementary external threads 50d
engaging the collar internal threads 56c for torsionally or threadingly
joining together the outer and inner fittings 56, 50.
The tubular shroud 50a illustrated in FIG. 3 is preferably fixedly joined
at its bottom end to the ballnose 50c and spaced radially outwardly
therefrom to define an annular slot 50e therearound for receiving the
collar portion 56b of the outer fitting 56.
As shown in FIG. 3, the collar 56b extends coaxially from an integral nut
56d upon which a conventional wrench may engage for turning the outer
fitting 56 to threadingly engage the inner fitting 50 in a conventional
manner. The outer fitting 56 is generally in the form of a conventional
B-nut suitably modified for the present invention. The nut 56d surrounds
the ferrule 56a in a conventional manner so that it may be rotated around
the centerline axis of the ferrule 56a as the threads engage to
correspondingly sealingly engage the ferrule 56a with the ballnose 50c and
provide a fluid-tight seal thereat. Torsional reaction loads from the
outer fitting 56 are carried through the splines 50b and 54c into the
mounting adaptor 54 and in turn into the combustor case 24. In this way,
torsion applied to the nut 56d does not twist the relatively fragile inlet
stem 46 itself, with the adaptor 54 providing a convenient element for
torsionally restraining the inner fitting 50 without requiring internal
access by an assembly technician within the combustor case 24 therefor.
Furthermore, the mounting adaptor 54 permits unrestrained differential
radial movement between the inner fitting 50 and the adaptor 54 itself
during operation to reduce undesirable thermal stresses in these
components. Different operating temperatures through the regions of the
fuel injection assembly cause the different components thereof to heat and
cool at different rates and undergo differential thermal expansion and
contraction. The shroud splines 50b engage the sleeve splines 54c to
prevent torsional movement therebetween while allowing relative axial
movement along the splines themselves, which in the FIG. 3 embodiment is
directed in the radial direction relative to the centerline axis of the
engine. In this way, as the ring manifold 42 expands and contracts
relative to the combustor case 24, the attached inlet stems 46 move
radially therewith, with the splines allowing unrestrained differential
radial movement to thereby reduce thermal stresses which would otherwise
be provided if the outer fittings 50 were radially attached or restrained
by the combustor case 24.
Furthermore, the outer fitting 56 preferably extends through the centerbore
of the adaptor 54 and is carried with the inner fitting 50 to which it is
attached. The outer fitting 56 is not separately attached to the adaptor
54 for allowing unrestrained differential radial movement therebetween.
As shown in FIGS. 2 and 7, means are disposed radially between the manifold
42 and the combustor case 24 for supporting the manifold 42 axially,
tangentially, and radially while permitting unrestrained differential
radial movement therebetween. Since the inlet stems 46 at the respective
inner fittings 50 are radially unrestrained due to the cooperating splines
described above, it also desirable to support the manifold 42 itself
without creating undesirable radial restraint which would cause
undesirable thermal strain and stress.
In a preferred embodiment as illustrated in FIGS. 2 and 7, the manifold
supporting means include a plurality of circumferentially spaced apart
tubular lugs 62a integrally extending radially outwardly from the manifold
42, and a respective plurality of pins 62b are fixedly mounted to the
combustor case 24 and extend radially inwardly in part into respective
ones of the lugs 62a. As shown in FIG. 7, each of the pins 62b is
integrally attached to a mounting plate 62c which is suitably attached to
the combustor case 24 using fasteners or machine screws 60, with each pin
62b extending radially inwardly through a corresponding port in the case
24 to radially slidingly engage a complementary bore in the lug 62a.
Since the lugs 62a and pins 62b are generally equally spaced around the
circumference of the manifold 42 as illustrated in FIG. 2, they support
the manifold 42 axially and radially and prevent torsional movement
thereof about the engine centerline axis 12. However, the pins 62b are
free to slide radially within the lugs 62a for allowing unrestrained
differential radial movement between the manifold 42 and combustor case 24
during operation. In this way, the manifold 42 is rigidly and accurately
positioned in space adjacent to the combustor dome 20c for accurately
positioning the respective fuel injectors 44 in their respective swirlers
36 for improving both SFC and NOx emissions.
As indicated above, with respect to FIGS. 1 and 3, a substantial pressure
drop exists across the combustor case 24 due to the difference in pressure
between the compressor discharge air 26 and the fan bypass air 32.
Accordingly, suitably means are provided for sealing the adaptor 54 to the
combustor case 24 against the differential pressure radially across the
combustor case 24. And, additional means are provided for sealing the
inner fitting 50 to the adaptor 54 against the differential pressure
across the combustor case 24 to thereby prevent leakage of the high
pressure compressed air 26 through the mounting port 52 and into the
bypass duct 30.
As shown in FIG. 3, the first sealing means for the adaptor 54 preferably
include a conventional split C-ring seal 64 mounted in compression between
the mounting flange 54a and a corresponding counterbore in the combustor
case 24. In this way, when the adaptor 54 is fastened in position to the
combustor case 24, the ring seal 64 is compressed in its counterbore for
providing an effective seal against leakage of the high pressure
compressor discharge air 26 from the combustor case 24.
The second sealing means for the inner fitting 50 preferably includes a
conventional split piston ring seal 66 mounted in compression between a
corresponding groove in the external surface of the shroud 50a and the
smooth internal surface of the sleeve 54b. Both seals 64, 66 are made of a
suitable metal for the hot environment of the combustor, with the ring
seal 64 sealing the outer surface of the adaptor 54, and the ring seal 66
sealing the inner surface of the adaptor 54 against leakage of the
pressurized air 26 therepast. The second ring seal 66 is preferably
disposed inside the sleeve 54b radially between the mounting flange 54a
and the sleeve splines 54c or allowing the shroud 50a to travel
longitudinally like a piston within the sleeve 54b, with the second ring
seal 66 providing effective piston sealing.
If desired, the outer fitting 56 may include a suitable annular groove
between the collar 56b and the nut 56d in which a third split piston ring
seal 68 is disposed for engaging the inner bore of the mounting flange 54a
in compression therewith for effecting a redundant seal through the
mounting adaptor 54.
Other sealing arrangements between the inner fittings 50 and combustor case
24 may be used including suitable gaskets or shims placed between the
underside of the mounting adaptor flange 54a and the combustor case 24.
Significant advantages accrue to the improved internal manifold fuel
injection assembly 10 disclosed above. The design is relatively easy to
manufacture and assemble. All piece parts of the assembly may be readily
made using conventional metal castings and joined together as required by
simple welds or brazes. The configuration may be scaled for any size
tubing and may readily fit in any size combustor case. The improved design
significantly increases the accuracy of position of the individual fuel
injectors 44 relative to each other about the common manifold 42 which
provides a reference support. Manufacturing stack-up tolerances of
assembling individual fuel injectors separately to a combustor case are
therefore eliminated, which eliminates the corresponding assembly stack-up
tolerances associated therewith. And, the manifold 42 more accurately
follows thermal radial movement of the combustor 20 to more accurately
inject fuel thereto.
Individual fuel injectors are no longer individually assembled through
corresponding mounting ports in the combustor case. Accordingly,
substantially fewer holes are required in the combustor case 24 since all
of the fuel injectors are instead directly attached to the internal
manifold 42 within the combustor case 24 and therefore do not require
separate mounting holes therethrough. Only one or two mounting ports 52
are required in the case 24 for providing fuel flow through the
corresponding inlet stems 46. This increases the simplicity of the
combustor case 24 and reduces stress concentrations therein for enhanced
life.
The mounting adaptor 54 with its internal splines 54c provides a simple and
convenient mechanism for torsionally restraining the inner fittings 50 so
that the outer fitting 56 may be tightened thereto without imposing
undesirable torsional loads on the ballnoses 50c and inlet stems 46 joined
to the manifold 42.
The several ring seals 64, 66 and 68 provide various levels of sealing
effectiveness to prevent leakage of the high pressure compressor discharge
air 26 from the combustor case 24 into the bypass duct 30.
The fuel circuit from the supply conduit 58 to the manifold 42 is
effectively leak proof using the standard ballnose joint effected between
the ferrule 56a and the ballnose 50c. In the event, however, of fuel
leakage at this joint, the shroud 50a provides a secondary fuel leakage
seal at the second ring seal 66 since the shroud 50a is integrally joined
to the bottom of the ballnose 50c and provides an impervious barrier
between the fuel joint at the ballnose and the sleeve 54b. Any leaking
fuel from the fuel joint will be directed through the mounting port 52
inside the sleeve 54b to outside the combustor case 24 instead of leaking
inside the combustor case 24.
As indicated above, all of the improved features associated with the first
manifold 42 may also be incorporated in the second manifold 42B
illustrated in FIGS. 1 and 2. If desired, both manifolds 42 and 42B could
be supplied with fuel from common instead of separate inlet stems 46 if
desired.
While there have been described herein what are considered to be preferred
and exemplary embodiments of the present invention, other modifications of
the invention shall be apparent to those skilled in the art from the
teachings herein, and it is, therefore, desired to be secured in the
appended claims all such modifications as fall within the true spirit and
scope of the invention.
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